Method of refining waste oils

ABSTRACT

THE REMOVAL OF SOLID PARTICAL IMPURITIES FROM WASTE OILS IS PERFORMED BY CONVENTIONAL MEANS AFTER THE IMPURITIES HAVE BEEN BROUGHT TOGETHER INTO A MASS TO SUCH AN EXTENT AS TO BE CAPABLE OF FILTERING, THE AGGREGATION BEING EFFECTED BY AN ELECTRIC SPARK TAKING PLACE IN THE WASTE OIL HAVING A DIELECTRIC MEDIUM THEREIN.

Aug, 8, 1972 WATARU ISHIBASHI 3,532,807

METHOD OF REFINING WASTE OILS Filed March 3, 1970 Indenlor WA'I'ARM ISHI BASHI Hrs ATTORNE United States Patent 3,682,807 METHOD OF REFINING WASTE OILS Wataru Ishibashi, 1563 Ichimiyake Yasucho, Yasugun, Shigaken, Japan Filed Mar. 3, 1970, Ser. No. 16,071 Int. Cl. B03c /00; B01k 1/00; C22d 7/08 US. Cl. 204-188 5 Claims ABSTRACT OF THE DISCLOSURE The removal of solid particle impurities from waste oils is performed by conventional means after the impurities have been brought together into a mass to such an extent as to be capable of filtering, the aggregation being effected by an electric spark taking place in the waste' oil having a dielectric medium therein.

This invention relates to a method of refining waste oils, and more particularly to a method of removing from waste oils, solid particle impurities in suspension, such as residual carbon and ash contents, by aggregating them into a mass by means of spark discharges taking place in the oil, whereby to ensure ready removal by ordinary means, such as a filter.

In general, a used oil, such as a lubricant, contains carbonaceous particles (residual carbon) and broken pieces of metal (ash contents). There have been prior proposals for removing such impurities, among which are the following: Firstly, a physical or mechanical method has been proposed, in which a mechanical device such as a centrifugal separator, a filter press, or a distiller is employed. Secondly, a chemical method has been proposed, in which a particular solution is used, such as an aqueous solution of a mineral acid (e.g. sulfuric acid), an aqueous solution of chlorine, caustic alkali, or ammonia. The former method has disadvantages in that the degree of refinement and the yield are insufficient and inadequate for commercial uses, and the latter method has problems of danger and difiiculty involved in operation of the equipment and the performance thereof, particularly in the case where sulfuric acid is used, which undesirably tends to react with the additive contained in the lubricant.

It has been found that the carbon particles present in the oil can be brought together into a mass when spark discharges take place between electrodes through a medium of grains of electrically conductive material immersed in the oil to be refined, the thus aggregated mass of carbon particles being readily removable by ordinary means such as a centrifugal separator or a filter press, thus eliminating the problem of remainders.

More specifically, in accordance with the invention, a pair of electrodes are immersed in the oil to be refined, the oil being charged with grains of electrically conductive material such as carbon particles immersed in the oil. A sparking voltage is impressed across the electrodes by a high frequency oscillating circuit, thus causing sparks between the grains. The grains are mutually in contact through respective coverings of thin oily film. The oily film is broken down by the spark impacts, causing decomposition (cracking) of the oil, carbon being segregated and gases formed. Simultaneously the surfaces of the grains are electrically eroded to small pieces by dint of the spark impact and spark discharge energy. As a result, the segregated carbon and the peeled-off carbon thus produced (hereinafter called carbon particles) are gradually brought together in the electrical field Where the spark discharges take place, in addition to which the residual carbon and ash contents originally present in the oil are aggregated into a mass to such an extent as to be readily 3,682,801 Patented Aug. 8, 1972 "ice filtered and separated from the refined oil by conventional means, which fact has been confirmed through an electron microscope. The oil may contain active powders such as active alumina or active clay, around which the aggregation will take place.

The principle underlying the present invention has not been clarified in respect to the reason why the carbon particles newly produced by the spark discharges in the oil participate in the aggregation with the carbonaceous particles originally present in the oil, but according to the known theory that a substance in the nascent state is relatively active, it can be postulated that the carbon particles are active immediately after segregation and separation from the grain surfaces, and that they participate in the aggregation with the carbonaceous particles originally present in the oil. Additionally, in view of the large impact pressures involved in the spark discharges, these pressures serving to disperse the carbon particles newly produced in the reactive system, and to distribute and mix all the substances present therein, it is believed that the spank discharge provide favour-able conditions under which the carbon particles are sure to collide with each other, resulting in smooth aggregation of the substances into a mass. It can further be reasoned that in the present apparatus the spark discharges take place in a pulse pattern in the oil to be treated, as the result of the use of an oscillating circuit of high frequency, the carbon particles being placed under the electromagnetic influence while in a potentially very aggregative state. It will be understood, as well, that as the carbon particles are produced in the oil in the absence of air, they are protected from the reduced reactivity otherwise caused by air, which factor results in further facilitation of their aggregation.

The invention will now be more particularly described by way of example, with reference to the accompanying drawing which schematically shows an example of equipment employed in carrying out the present invention.

A pair of electrodes 2 and 3 are installed in an oil tank 1 made of an electrically insulating material and into which oil 4 is placed for refinement, such oil containing residual carbon and ash contents to be removed. The oil tank 1 is connected to a high frequency oscillating circuit 5 outside the tank.

In the preferred example illustrated, a quenched sparkgap oscillator is employed in order to ensure an increased frequency of discharges per unit time. Spark gaps 11 are connected in series with the electrodes 2 and 3. The circuit 5 has terminals 6 and 7 for connection to a commercially available power supply, a step-up transformer 8, a limiting resistor 9, a charge-discharge capacitor 10, the spark discharge gaps 11, an oscillating inductance 12, an inductance 13 connected in parallel with the electrodes 2 and 3 to ensure effective spark discharges, choke coils 14, 15 and resistors 16 and 17.

In the tank 1 there is a gas outlet duct 18 to vent gas generated by the refining of the oil. Grains A of electrically conductive material are supplied to form a dielectric medium through a hopper 19, the oil being introduced through an inlet opening 20. The treated oil is discharged through an outlet opening 211.

In the system thus constructed, the oil tank 1 receives carbonaceous coarse grains A, whose size ranges from 5 mm. to 20 mm., immersed in the oil to be refined. Subsequently, a discharge voltage of high frequency is impressed across the electrodes 2, 3 by the oscillating circuit 5 to cause sparks between the grains A, so that powder-like carbon particles are separated from the surface of each grain under the urging of the spark energy. Simultaneously, further carbon particles are segregated through decomposition of the oil, together with gases, the latter being evacuated from the system through the duct 18, the former being deposited in the oil within the tank 1. The two kinds of carbon are violently agitated and mixed under the impact pressure of the sparks, which pressure causes individual grains to move to and fro in a continuous manner. This action causes changes of flashpoints continuously, thereby preventing problems of local overheating and permitting uniform admixture of the carbon particles, which effect constitutes a valuable feature of the present invention in which spark discharge are used. As the sparks are repeatedly generated in a pulse pattern, the carbon particles increase in amount with time. Consequently, aggregation of them progresses as time advances.

EXAMPLE 1 In all the examples given hereinafter, a motor oil was used as the waste oil to be refined.

Dimensions of the oil tank: 200 mm. (diameter) by 1000 mm. length Material of the oil tank: polypropylene Material of the electrodes: graphite Size of the electrodes: 20 mm. by 100 mm.

Spacing of the electrodes: 800 mm.

Source voltage: 220 v.

Discharge voltage: 20 kv.

Discharge frequency: 40 khy.

Freqencies of discharges: 6 per /2 cycle Electricity consumed: 40 kwh.

Amount of carbonaceous grains: kg. (substantially immersed in the oil) Average size of the grains: 9.5 mm.

Amount of refinement: 600 l./hr.

Amount of oil consumed through cracking: 3.3 l./hr.

Amount of segregated carbon through cracking: 1.3

kg./hr.

Amount of separated carbon from the grain surface: 1.5

kg./hr.

Size of particles in suspension in the waste oil: 25 millimicrons to 2.5 micron Size of particles in suspension after treatment: 15 micron to 40 micron The following is a comparison of properties between the starting material, waste oil and the refined oil, where refined oil means oil free from suspended particles of impurities that were removed by a filter press after treatment by spark discharges.

Waste oil oil Residual carbon (percent) 2.810 0. 159 Ash contents (percent) 0. 525 0. 005 Density 15 (4 C.) s 0. 899 0. 889 Viscosity (centistoke, 50 C.) 57.0 46. 7

EXAMPLE 2 Dimensions of the oil tank: 200 mm. (diameter) by 1000 mm. length Material of the oil tank: polypropylene Material of the electrodes: graphite Size of the electrodes: mm. by 100 mm.

' Spacing of the electrodes: 800 mm.

Average size of the active powder: 40 micron Amount of the active powder added to the waste oil: 5%

of the oil (by weight) Dielectric medium: sintered graphite Amount of the dielectric medium: 15 kg. (immersed in the oil) Average size of the dielectric medium: 10 mm.

Amount of refinement: 1000 l./hr.

Amount of the material oil consumed through cracking:

Amount of segregated carbon through cracking:

kg./hr.

Size of particles in suspension in the waste oil: 25 millimicron to 2.0 micron (confirmed through an electron microscope) Average size of particles in suspension after treatment (aggregated particle): 45 micron Amount of separated carbon from the grain surface: 1.5

kg./hr.

The refinement characteristics are as follows, comparing the results derived from the method according to the invention, with those from the prior art method where sulfuric acid is used, wherein the property of the starting material oil is this:

Ash contents: 0.525%

Residual carbon: 1.201%

Water: trace Elementary analysis: C, 84.89%), H (12.82%)

The contrasting data is derived from the sulfuric acid method where the waste oil was heated at 185 under a pressure of 2-0 mm. Hg, to which sulfuric acid was added in the proportion of 50 kg. to 1 kl., and kept as it was for 24 hours, so that sulfuric acid sludge was formed in deposits, which, subsequently, was stirred at a temperature of centigrade in the presence of activated clay in the proportion of 45 kg. to 1 kl., the latter being removed by means of a filter press.

The embodiments of the invention in which an exclusive property of privilege is claimed are defined as follows:

1. A method of refining waste oil containing solid particle impurities therein which method comprises the steps of:

(a) Immersing a pair of electrodes into the waste oil to be refined;

(b) Charging the waste oil with coarse grains of elec trically conductive material,

(0) Impressing a pulsating discharge voltage of high frequency across the electrodes such that sparking is effected between said coarse grains so that carbon particles are formed thereby with said carbon particles causing aggregation of the solid particle impurities contained within the waste oil, and

(d) Separating the aggregated particles of impurities from the refined waste oil.

2. A method according to claim 1 wherein the coarse grains are powdered carbon.

3. A method according to claim 1 wherein an active 3,433,728 3/1969 Petroff 204-228X powder is added to thewaste oil. 2,826,540 3/ 1958 Keeleric 204143 G 4. A method according to claim 1 wherein an activated clay is added to the waste oil as an active powder. FOREIGN PATENTS 5. A method according to claim 3 wherein the active 5 powderisan active a1umina 494,153 10/1938 Great Britain 204-188 JOHN H. MACK, Primary Examiner N. A. KAPLAN, Assistant Examiner U.S. Cl. X.R.

References Cited UNITED STATES PATENTS 3,494,762 2/1970 Ishibashi 204-312X 3,491,010 1/1970 Ishibashi 204171 204-171, 323 

